Fig. 4: Stability test and response time measurements of UFPTs.
a D(E)-hysteresis curve of an UFPT before, during and after bending over an 80-µm-thick gold wire. Durability testing under (b) transversal-load and (c) longitudinal-strain conditions. b Current response when a transducer mounted on a glass carrier is subjected to repeated transversal compression and release via a stamp over a period of more than 5 h (>6000 cycles). c Current response upon longitudinal strain cycling over more than 1000 periods. The inset schematically illustrates the longitudinal tensile test procedure. First, the UFPT was mounted on a 20% pre-strained rubber carrier, which was clamped at both ends. Then, by periodically relaxing and stretching the carrier (light blue) over an interval of 0–20% strain, the transducer (purple) was contracted or retracted, respectively. d Time dependence of the charge response of the UFPT for a trapezoidal transversal load with a top force level of 6 N and a rise time of « 20 ms N−1. The charge response signal (black) precisely follows the force profile (red).
